Prehistoric Rodents With Brains The Size of Primates!

If new U of T research on the brains of an ancient rodent tells us anything, it's that bigger does not necessarily mean better.

Paramys was a large rodent by modern standards - about three kilograms, roughly the size of a small cat - that lived during the mid-Eocene, some 47 to 49 million years ago.

"The brain was certainly larger than we expected considering the time period," says Bertrand. "Even more surprising is that it [the brain] was almost as large, and in some cases larger, than primitive primates of the same time period."

The key difference is that Paramys was relatively smaller than even the most primitive primates in the neocortex region, the part of the brain that deals with "higher" brain functions like sight and hearing.

"This tells us that something is going on in the neocortex of early primates that is not observable in early rodents. " says Bertrand. "The changes in the neocortex of rodents occurred later in time and with less intensity than in primates." PR